I'd like some clarification there.
We all know the Mixamp only supports DH2 mode for Dolby Headphone, which adds a bit of reverb. Do you use the Xonar cards in DH1 mode (which doesn't add any reverb at all)?
I don't know if the actual sound quality on the Essence cards is actually better to an audible extent, but it's said that the Titanium HD has a "warmer" sound signature with a bit more bass emphasis by comparison. I can believe that, since the bass does seem a bit punchier than the X-Fi Prelude and X-Fi Forte I had been using prior.
The reason why I generally recommend X-Fi cards for anyone who cares about old games that use the DirectSound3D or OpenAL APIs is twofold:
- EAX 3/4/5 support. The most DS3DGX or Xear3D on a C-Media card might do is try to emulate those higher versions, but it probably won't sound as intended. Do note that practically everything has proper EAX 1/2 support, though.
- CMSS-3D Headphone is capable of using the 3D positional information the DS3D and OAL APIs provide to provide the user with a true 3D binaural mix, very much like Aureal did with A3D and their Vortex sound card chipset back in the late 1990s. By comparison, Dolby Headphone would have to have that 3D information downmixed to 7.1 before it applies its binaural effects, so you lose all sense of height, and sounds seem to jump between speaker positions a bit more instead of panning smoothly, especially toward the rear. (Not surprisingly, this general emphasis on 7.1 surround sound in gaming at the expense of true 3D sound solutions is a constant point of irritation for me.)
But if the only games you play all use XAudio2 + X3DAudio or FMOD Ex anyway (software-processed, limited to 7.1 at the most), then those advantages largely go out the window and you might be a little more satisfied with a C-Media card like a Xonar Essence STX or an HT Omega Claro Halo, especially if you plan to make use of the built-in headphone amplifiers at less cost than buying an external, dedicated amp. (Such amplifiers don't do me any good now that I've taken the route of Stax and electrostatics in general, though; that's something you may want to consider as you plan your audio upgrade path.)